Radio access networks (RANs) provide for radio communication links to be arranged within the system between a plurality of user terminals. Such user terminals may be mobile and may be known as ‘subscriber units’ or ‘subscriber units.’ At least one other terminal, e.g. used in conjunction with subscriber units, may be a fixed terminal, e.g. a control terminal, base station, eNodeB, repeater, and/or access point. Such a RAN typically includes a system infrastructure which generally includes a network of various fixed terminals, which are in direct radio communication with the subscriber units. Each of the fixed terminals operating in the RAN may have one or more transceivers which may, for example, serve subscriber units in a given local region or area, known as a ‘cell’ or ‘site’, by radio frequency (RF) communication. The subscriber units that are in direct communication with a particular fixed terminal are said to be served by the fixed terminal. In one example, all radio communications to and from each subscriber unit within the RAN are made via respective serving fixed terminals. Sites of neighbouring fixed terminals may be offset from one another or may be non-overlapping or partially or fully overlapping.
RANs may operate according to an industry standard protocol such as, for example, the Project 25 (P25) standard defined by the Association of Public Safety Communications Officials International (APCO), or other radio protocols, such as the terrestrial trunked radio (TETRA) standard defined by the European Telecommunication Standards Institute (ETSI) or the Digital Mobile Radio (DMR) standard also defined by the ETSI. Communications in accordance with any one or more of these standards, or other standards, may take place over physical channels in accordance with one or more of a TDMA (time division multiple access), FDMA (frequency divisional multiple access), or CDMA (code division multiple access) protocol. Subscriber units in RANs such as those set forth above send user communicated speech and data, herein referred to collectively as ‘traffic information’, in accordance with the designated protocol.
Many so-called ‘public safety’ RANs provide for group-based radio communications amongst a plurality of subscriber units such that one member of a designated group can transmit once and have that transmission received by all other members of the group substantially simultaneously. Groups are conventionally assigned based on function. For example, all members of a particular local police force may be assigned to a same group so that all members of the particular local police force can stay in contact with one another, while avoiding the random transmissions of radio users outside of the local police force group. Many of these ‘public safety’ RANs have been deployed in dense urban and suburban areas.
Same or similar wireless communication systems may be used in more remote areas of the country, such as rural areas, where events occur less often, where a large number of sites provide service over a large geography containing few users, where fewer resources are generally available, and where operating costs may be a larger concern given the reduced number of occurrences for which each wireless communication system is needed. For example, many current trunked systems require a radio site to continuously be “on” such that a fixed terminal in the trunked site is continuously on the air and a control channel is continuously being transmitted. This allows radios that are within the proximity of the trunked site to be able to identify the trunked site, switch to the trunked site when needed, and receive and transmit control information, including, for example, new call requests, over the control channel of the trunked site.
However, a significant drawback of continuous, periodic, or intermittent required broadcasts is that it may cause unnecessary power consumption (which may be costly) when the radio site is not currently being used. This problem may be exaggerated in lower density regions where incidents occur with less frequency. However, such radio systems may be used in emergencies, and so still must be highly available. Accordingly, what is needed is an improved method for conserving resources in lower density regions while still providing for the high performance and high availability required of emergency response radio systems.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present disclosure.